Conventional electrodes for measuring electrophysiological signals like EEG, EMG and ECG may be attached to the skin of the patient by means of an adhesive. Generally, a gel may be used to ensure a good galvanic contact between the electrode and the body. The adhesive and the gel can cause skin irritation and are uncomfortable for continuous monitoring.
An alternative to such electrodes are capacitive sensors where the capacitive coupling between the skin and an electrode is used to measure surface potentials. Such capacitive sensors are disclosed in US 2011/0248729 which describes a sensor system and method for the capacitive measurement of electromagnetic signals having a biological origin. Capacitive sensors for electro-physiological measurements suffer from motion artifacts due to the time-varying distance between capacitive electrode and the body or skin. In many applications such motion artifacts may present problems.